Industrial filter with arrangement for removing machining chips from coolant prior to filtering

ABSTRACT

An arrangement for removing chips from a machining coolant prior to filtering out the finer solids in a main filter. A coarse weave belt is frictionally driven along a strainer bottom wall of an auxiliary tank suspended above the main filter tank, the permanent media belt of a coarse weave which allows the liquid and suspended finer solids to pass through while capturing the chips. A powered drag conveyor frictionally engages and drives the permanent media belt through the auxiliary tank, each diverging when returning across the top and bottom respectively of the auxiliary tank prior to being recirculated through the auxiliary tank.

BACKGROUND OF THE INVENTION

[0001] This invention concerns industrial filters used primarily inmetalworking plants to filter machining coolants to remove chips,grinding and tool wear detritus, etc., so that the coolant can bereused.

[0002] These solids to be removed include large volumes of machinedchips of relatively large size, and a smaller volume of much finerparticles. Vacuum filters are widely used to filter such liquids, andinvolve the use of woven belts overlying a perforated top vacuum boxdisposed at the bottom of an open tank which receives the coolant to befiltered.

[0003] Disposable sheet paper media is sometimes used to improve filterperformance overlying the belt, which collects the solids and isperiodically indexed out for disposal. Disposal of the paper mediacreates a maintenance labor burden as well as an environmental burden.

[0004] The vacuum box draws the coolant through the porous belt and/ordisposable media to be filtered. The filter belt is typically overlainwith a drag conveyor which is periodically advanced to moveaccumulations of chips on top of the belt out of the tank. The beltitself is periodically indexed with the conveyor so as to be able to bewashed to clean off the filtrate. The more frequent the filter belt isindexed, the shorter its service life, and the index cycle itselfinterrupts filter operation reducing its capacity. Some build-up offiltered solids is desirable as this improves the clarity of thefiltered liquid, as the filter “cake” acts as an additional filteringmedia. Frequent indexing reduces this beneficial effect as the solidsaccumulation is reduced. The machining chips rapidly accumulate in largevolumes if left in the coolant when filtered, which necessitatesfrequent indexing. The presence of sharp metal chips on the belt alsomay cause the drag conveyor to tear holes in the belt by pulling thesharp metal chips along the belt surface.

[0005] It has therefore previously been recognized that it isadvantageous to remove the machining chips prior to filtration to removethe fine solid particles from the used coolant.

[0006] When iron and steel chips are involved, settling tanks ahead ofthe filter have been used effectively, as these chips are heavy andsettle out rapidly. Magnetic separators have also been used to removeiron and steel chips prior to filtration by vacuum filters.

[0007] However, in the auto and other industries, machining of aluminumhas become much more widespread. Aluminum chips, being much lighter, donot settle out as well such that this approach is not effective.Magnetic separators likewise do not work with aluminum chips.

[0008] For these applications, passing the liquid through a wedgewire orperforated plate strainer has been employed to remove the chips prior tofiltration in a main filter. Wedgewire is made by welding triangular insection strands of wire in parallel spaced apart arrays ontotransversely extending bars to provide a slotted strainer plate. Theused coolant containing the chips is directed into a smaller tank whichhas a wedgewire bottom plate mounted within in the upper part of thevacuum filter tank. The liquid passes out of the smaller tank throughthe wedgewire bottom plate and passes into the main filter tank, leavingmost of the chips behind. A drag conveyor is continuously moved alongthe wedgewire bottom plate to carry away the chips accumulating abovethe wedgewire plate.

[0009] While this arrangement does remove most aluminum chips, if thewedgewire strand spacing too close, some of these chips tend to bejammed into the spaces, this tendency exacerbated by the action of thedrag conveyor flights which tend to push the chips into the spaces andto deform the exposed ends over, making it difficult to clear thesechips from between the wedgewire strands.

[0010] Over time, the wedgewire becomes clogged, and this necessitatesperiodic extended shutdowns to access the wedgewire bottom plate forcleaning. It is a difficult and time consuming process to remove theaccumulated jammed chips.

[0011] For this reason, the wedgewire spacing has been increased in anattempt to minimize the tendency for clogging the same with the chips,but in this situation, many chips pass through to the filter belt,increasing the rate at which indexing must be done. If indexing is donemore frequently, this reduces the average accumulation of fine solids onthe belt, and this in turn decreases the clarity of the filteredcoolant.

[0012] It is the object of the present invention to provide anarrangement for removing machining chips from used coolant prior tofiltering the coolant in a vacuum filter, which arrangement effectivelyremoves a very high proportion of the chips from the coolant, whicharrangement is effective for removing aluminum chips, and which does notentail a substantial maintenance burden.

SUMMARY OF THE INVENTION

[0013] The above object and others which will be understood upon areading of the following specification and claims are achieved byproviding a recirculating coarse weave permanent filter belt which runsover the top of a strainer plate forming the bottom of an auxiliary tanksuspended in the upper region of a main filter tank. The wedgewirestrand spacing is wide enough to minimize any tendency to capture themachining chips. The permanent filter belt is returned around the bottomof the auxiliary tank. The filter belt weave is open enough to allow thesuspended solids to freely pass through with the used coolant whilecapturing a great proportion of the metal chips. The filter belt isfrictionally driven by engagement with a continuously driven drag flightconveyor which runs along the upper surface of the belt, and returnsback over the top of the auxiliary tank in being recirculated, so as todiverge from the filter belt when both are being returned. The belt ispreferably a coarse twill weave with the “one over” side engaged by theconveyor flights to establish a nonslipping positive engagement with thebelt so that any tendency to drive the chips into the belt is avoided.The secure engagement between the conveyor flights and the filter beltallows the belt to be reliably driven without slippage despite beingpressed onto the wedgewire tank bottom by the weight of the coolantliquid and chips bearing on it. The divergent return paths of the flightconveyor and filter belt insure that different belt areas contact theflights when engagement occurs to distribute the belt wear resultingfrom engagement with the conveyor flights, which, together with thenonslip engagement therebetween, greatly increases the filter beltservice life.

[0014] A sloping shed plate is interposed below the wedgewire plate andthe return section of the filter belt to allow the liquid passingthrough the filter belt and wedgewire plate to be directed to eitherside of the permanent filter belt and into the main filter tank.

[0015] A variable speed drive from the flight conveyor enables a manualor automatic variance in conveyor speed to accommodate changes in thechip load.

[0016] The fine solids passed through the chip removing arrangement arethus allowed to build up on the primary filter belt to improve theclarity of the filtered liquid, as the primary filter does not need tobe indexed nearly as often as with the prior arrangements due to thegreat reduction in chip volume that must be handled by the main filter,which result increases the service life of the main filter permanentfilter belt.

DESCRIPTION OF THE DRAWING FIGURES

[0017]FIG. 1 is a diagrammatic representation of a vacuum filtercombined with an arrangement according to the invention for prefilteringremoval of machining chips.

[0018]FIG. 2 is a plan view of the apparatus shown in FIG. 1.

[0019]FIG. 3 is a fragmentary cross-sectional view of a portion of theapparatus shown in FIG. 1.

[0020]FIG. 4 is an enlarged side view of the engagement of the dragconveyor flights and the permanent media belt included in the chipremoval arrangement according to the present invention.

DETAILED DESCRIPTION

[0021] In the following detailed description, certain specificterminology will be employed for the sake of clarity and a particularembodiment described in accordance with the requirements of 35 USC 112,but it is to be understood that the same is not intended to be limitingand should not be so construed inasmuch as the invention is capable oftaking many forms and variations within the scope of the appendedclaims.

[0022] The chip removal arrangement 10 according to the presentinvention shown in FIG. 1 is combined with a vacuum filter 12 of a typeshown in U.S. Pat. No. 5,624,579 by the inventor of the presentapplication.

[0023] A main tank 14 is provided to receive coolant to be filtered, butthe dirty liquid inlet trench 16 (FIG. 2) first enters an auxiliary tank18 associated with the chip removal arrangement 10, the coolant liquiddraining through a strainer bottom wall 20 (constructed of a wedgewireplate), and into the main tank 14.

[0024] The main filter 12 includes a permanent media belt 22 circulatedover the top 24 of a vacuum box which has openings (such as by awedgewire plate) allowing liquid to be drawn through the overlyingsegment of the permanent media belt 22 and into a vacuum box interior 26by a pump 28 returning clean liquid to the coolant supply system.

[0025] The permanent media belt 22 is recirculated up a sloping end wall30 of the main tank 14 by a frictional engagement with a segment of adrag conveyor 32 powered with a drive unit 34.

[0026] The permanent media belt 22 is recirculated around the bottom ofthe main tank 14 after passing through a scraper-washer 36 mechanism. Acollector hopper 38 is positioned below to catch the debris scraped fromthe permanent media belt 22 (and the disposable media if used asdescribed below).

[0027] The permanent media belt reenters the tank 14 out the other endof the main tank 14, passing down the tank vertical end wall 40. Thedrag conveyor 32 returns back over the top, supported by a series ofguides (not shown).

[0028] A disposable media roll (not shown) may be mounted above thatpoint to allow disposable media to be fed in between the drag conveyor32 and the permanent media belt 22 to be driven together with thepermanent media belt across the vacuum box 26, as described in U.S. Pat.No. 5,624,579.

[0029] The chip removal arrangement 10 according to the presentinvention includes the auxiliary tank 18 having the strainer bottom wall20.

[0030] An auxiliary permanent media belt 46 is arranged to befrictionally driven across the wedgewire bottom wall 20 by an auxiliarydrag flight conveyor 48 having a segment overlying the wedgewire bottomwall 20.

[0031] The auxiliary permanent media belt 46 is of a twill weavereferred to as “1 over, 2 under”, and of a coarse grade. The weave issufficiently open to allow the fine solids to freely pass through whilecapturing the chips, which are much larger. The spacings in thewedgewire bottom wall 20 are also sufficiently wide to allow the solidsto pass through (as well as any chips not captured by the belt 46). Thepermanent filter belt 46 has one side (the “one over” side) which willbe much more positively engaged by the inclined edge of the conveyorflights 50 (FIG. 4) which side is therefor arranged to be facing up overthe wedgewire strainer bottom wall 20. The flights 50 are preferablyinclined towards the direction of movement of the conveyor 48 as shown,as this has been found to improve the engagement therewith. This allowsthe permanent media belt 46 to be positively frictionally driven despitethe combined weight of the coolant and chips 49 bearing thereon. As iswell known, the orientation of the wedgewire strands 21 (FIG. 3), withthe flat of the triangle facing up also reduces wear on the permanentmedia belt 46.

[0032] The drag conveyor 48 and permanent media belt 46 together ascenda sloping exit wall 52 of the tank 18, diverging away from each other atthe top thereof, the permanent media belt 46 then recirculated backaround the bottom of the tank 18 guided on a series of guide rollers 54,while the drag conveyor 48 is returned back over the top of the tank 18.A variable speed drive 58 with a manual or automatic control 60 allowsthe speed of the drag conveyor 48 (and permanent media belt 46) to bevaried in correspondence to the chip load. The drive 58 preferablyoperates continuously to carry away the captured chips as theyaccumulate.

[0033] A belt washer header 62 (FIG. 2) is also preferably provided,with an array of spray nozzles 64 directed at the belt 46 as it ascendsthe rear wall of the tank 18 to keep it clear of accumulated solids,which are discharged into the used coolant in the main tank 12.

[0034]FIG. 3 shows a drain shield 66 disposed below the wedgewire 20 andserving to direct liquid around either side of the return segment 46A ofthe auxiliary permanent media belt 46.

[0035] The chips are discharged at the top of the sloping wall 52 as theflight drag conveyor 48 and permanent media belt 46 diverge and reversepaths, directed by a discharge guide chute 68 (FIG. 1) into a chiphopper 70 for further handling.

[0036] Accordingly, the chips are captured by the continuously movingdrag conveyor 48 and permanent media belt 46, such that chip build up inthe wedgewire plate 20 does not occur. The remaining solids, beingtypically present in much smaller volumes, do not need to be removed atfrequent intervals and a build up can be allowed. This produces enhancedclarity of the filtered liquid, and reduces the frequency of cycling ofthe filter belt 22 to increase its service life.

[0037] Since the drag conveyor 48 and permanent media belt 46 do notmove relative each other to any significant degree, wear of thepermanent media belt 46 is minimized, and driving chips into theauxiliary permanent media belt 46 is also avoided so that spray washingof the permanent media belt 46 can keep it clean. Since the conveyorflights 50 randomly engage different points on the permanent media belt46 when reengaging the same, the wear that does occur is distributedover the permanent media belt 46.

[0038] While a wedgewire strainer plate 20 is shown and preferred, otherstrainer plate configurations can be used, such as perforated plate, aslong as the openings are sufficiently large to allow passage of thesolids.

1. An arrangement for removing machining chips from a liquid prior tofiltering the same in a main filter having a main tank for receiving theliquid, said arrangement comprising: an auxiliary chip receiving tankmounted over said main tank having a bottom strainer wall havingopenings allowing liquid containing solids to pass freely through to bereceived in the main tank; a continuous loop of permanent media beltextending through said auxiliary chip receiving tank over said bottomwall and out of said auxiliary tank, and returned beneath said auxiliarytank; a powered drag conveyor circulated through said auxiliary tank infrictional engagement with said permanent media belt to advance thesame, said drag conveyor returned over the top of said auxiliary tank,said permanent media belt having a weave sufficiently open to allow saidliquid and solids to pass therethrough while capturing said chips,whereby said chips are removed therefrom and carried out of saidauxiliary tank to a collection point.
 2. The arrangement according toclaim 1 wherein said drag conveyor is continuously driven tocontinuously drive said permanent media belt to be recirculated throughsaid auxiliary tank.
 3. The arrangement according to claim 1 whereinsaid drag conveyor drive is variable speed to drive said drag conveyorand permanent media belt at varying speeds.
 4. The arrangement accordingto claim 1 wherein said strainer bottom wall is formed by lengthwiseextending spaced apart wedgewire strands.
 5. The arrangement accordingto claim 1 wherein said permanent media belt is of a one over two undertwill weave with said drag conveyor having flights engaged with said oneover side.
 6. The arrangement according to claim 1 wherein saidauxiliary tank is mounted within an upper region of said main tank. 7.The arrangement according to claim 1 further including a deflectorshield mounted between the underside of said bottom wall and said returnof said permanent media belt to cause liquid container solids passingthrough said bottom wall to drain to either side of said permanent mediabelt and into said main tank.
 8. The arrangement according to claim 1further including a belt washer directing jets of clean liquid at saidpermanent media belt prior to reentering said auxiliary tank.
 9. Thearrangement according to claim 1 wherein said auxiliary tank has asloping exit wall, up which said permanent media belt is driven by saiddrag conveyor in exiting said auxiliary tank.
 10. A method of removingmachining chips from a liquid to be filtered in a main filter having amain tank to remove fine solids suspended therein comprising the stepsof: suspending an auxiliary tank above said main tank, and providingsaid auxiliary tank with a bottom wall having openings configured toallow said liquid and suspended solids to drain therethrough; arranginga recirculating permanent media belt loop to have a segment passingthrough said auxiliary tank and overlying said bottom wall, of a weavecoarse enough to allow said liquid and suspended solids to passtherethrough but tight enough to capture said machining chips; drivingsaid permanent media belt with a powered drag conveyor frictionallyengaging said permanent media belt to drive the same and assistingcarrying off chips captured on said permanent media belt; directing saidliquid with said chips and finer solids onto said permanent media beltto capture said chips while allowing said liquid and suspended finersolids to drain through said permanent media belt and bottom wall andinto said main tank of said main filter for filtering out said suspendedfiner solids.
 11. The method according to claim 10 further including thesteps of recirculating said permanent media belt back across the bottomof said auxiliary tank and recirculating said drag conveyor back oversaid auxiliary tank to produce divergence thereof to cause frictionaldisengagement as said drag conveyor diverges and reengagementtherebetween as said drag conveyor reenters said auxiliary tank.
 12. Themethod according to claim 11 further including the step of continuouslydriving said permanent media belt with said drag conveyor.
 13. Themethod according to claim 12 further including the step of driving saiddrag conveyor at varying speeds in accordance with the rate of chipbuild up.
 14. The method according to claim 10 wherein said permanentmedia belt is of a twill weave with a one over two under weave andwherein in the said step of driving said permanent media belt with saiddrag conveyor, conveyor flight plates are engaged with said one overside of said permanent media belt.
 15. The method according to claim 10wherein in said step of providing said bottom wall spaced wedgewirestrands are arranged lengthwise to said permanent media belt.
 16. Themethod according to claim 11 further including the step of deflectingliquid and suspended solids to either side of said return segment ofsaid permanent media belt.